1. Field of the Invention
The present invention relates generally to power measurement circuits and systems, and more particularly to a power measurement system that provides for measurement of complex power, including reactive and real power delivered to a load.
2. Background of the Invention
Power measurements performed by integrated circuits (ICs), such as those used in motor control and power supply systems typically measure voltage and current delivered to a load using analog-to-digital converters (ADCs) and then compute a measured power level by multiplying the voltage and current measurements to obtain a power measurement. Systems such as those disclosed in U.S. Pat. No. 5,521,482 typically assume that the measured power is a real power value, or for A/C power measurements, use a power factor to adjust the power calculated from the voltage and current measurements to obtain the real power. Such power computations are accurate for a fixed-frequency stable sine wave. For DC power measurements, the power factor correction is not needed.
However, making accurate A/C power measurements when the frequency and/or amplitude varies rapidly, such as in some A/C motor control applications, and when jitter is present is very difficult and requires extensive computations in order to preserve accuracy of the measurements. Further, measurement of complex power including both real and reactive power metrics is desirable for total modeling of the load conditions which is useful in monitoring and controlling power delivery in applications such as motor control.
Therefore, it would be desirable to provide a less computation-intensive system and method for performing A/C power measurements. It would further be desirable to provide such a system and method that provides a complex power measurement output.